The proposed research is intended to define the structures of mRNAs encoding several of the high molecular weight prohormone forms of the neurosecretory products of the Caudal Neurosecretory Complex (CNC) of the goby Gillichthys mirabilis. We have complete or partial amino acid sequence information describing two secreted products of the CNC: Urotensin II (UII) a dodecapeptide with smooth muscle contracting activity and Caudal Neurosecretory Peptide (CNP) a peptide at least 72 amino acids long of unknown biological activity. In addition, we have immunohistochemical evidence that a third neuropeptide is present in the tissues: Urotensin I (UI), a long-acting vasodepressor. Using the techniques of molecular cloning, we have produced a cDNA library from Gillichthys posterior spinal cord which has been probed for mRNA encoding these three peptides. We have isolated and partially characterized a clone that encodes both UII and CNP. This proposal describes studies that will allow us to complete our analysis of the UII/CNP clone and to attempt to isolate and sequence a clone encoding UI. Knowledge of the prohormone structure that can be infered from this information can then be applied to our studies of the kinetics of prohormone to active product processing in the CNC. It is further proposed that we will define the structure of the gene for the UII/CNP molecule. This information will be used in this laboratory in the future to study the regulation of expression of this gene.